Systems And Methods For Tensioning Mooring Lines At The Seafloor

Abstract

Systems and methods are disclosed for deploying one or more anchor piles on the seafloor using submersible line tensioning systems and techniques to achieve tensioning of mooring lines at the seafloor rather than at the conventional vessel deck level. Among other things, the disclosed systems and methods may be advantageously employed for tensioning mooring lines for Mobile Offshore Drilling Units (MODUs) when additional mooring legs must be added to the original complement of MODU legs, as well as and for tensioning mooring lines for vessels having turret mooring systems, each of which have limited space for surface tensioning equipment.

Description

[0001]This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61 / 953,269, filed on Mar. 14, 2014 and entitled “SYSTEMS AND METHODS FOR TENSIONING MOORING LINES AT THE SEAFLOOR”, which is incorporated herein by reference in its entirety for all purposes.FIELD OF THE INVENTION[0002]This invention relates generally to mooring systems and methods for drilling vessels and other types of vessels.BACKGROUND[0003]Conventional mooring systems for Mobile Offshore Drilling Units (MODU), Floating Production Storage & Offloading (FPSO) and Floating Storage & Offloading (FSO) vessels rely on pre-tensioning of their respective mooring lines by means of winches, windlasses or chain jacks mounted on the vessel itself. Mounting of mooring line tensioning equipment on the deck of a vessel is generally not a problem for a MODU or a FPSO or FSO that is equipped with a spread mooring. However, deck-mounting of tensioning equipment may be difficult or impossible under some circ...

AI Technical Summary

Benefits of technology

The patent describes a system and method for tensioning mooring lines on seagoing vessels at the seafloor rather than on the vessel itself. This is achieved using submersible mooring line tensioner equipment that is positioned away from the vessel and is either permanently associated with individual anchor structures or can be moved from one anchor structure to another. This approach reduces the carbon footprint of the vessel and can be used on vessels without any mooring line winches or tensioning equipment. The system includes a modular and submersible mooring line tensioner that can be temporarily installed on a submerged anchor structure and manipulates the mooring line to tighten it between the vessel and the anchor. The tensioner may include integrated actuators powered by an external or internal power source. The method involves coupling segments of the mooring line to the vessel and using the submersible line tensioner to apply tension to the mooring line between the vessel and a submerged anchor pile embedded in the seafloor.

Problems solved by technology

However, deck-mounting of tensioning equipment may be difficult or impossible under some circumstances, such as when a MODU needs to add additional mooring legs (e.g., for compliance with requirements by the Bureau of Safety and Environmental Enforcement (BSEE) for drilling in the Gulf of Mexico during the hurricane season), and when a FPSO or FSO is equipped with an internal or external turret mooring system.

For example, in the case of a MODU originally designed for eight mooring legs, but that now requires twelve mooring legs, it is often difficult to accommodate four more tensioning systems and associated chain lockers required for the four additional legs.

In the case of a FPSO or FPO with a turret mooring system, it is very difficult to mount mooring tensioning equipment on the turret due to lack of space.

Images